WordPress MU

Not sure if this is a Wordpress MU caused issue or server issue, but our web hosting buddies told me to check here. My users can upload .docx files to there posts, but when someone goes to download them, they somehow convert to .doc. I can't find documentation on this happening to anyone else anywhere.

Elsewhere on our site on the same server, we are able to upload docx files for download with out any problem. In fact, the link to download the docx files are in a regular single user install of Wordpress. We did have to modify the root htaccess file to get that to work properly with some mime information.

The only think I can think of is maybe the subdomain usage of Wordpress MU is affecting things, but even then I would have no idea how. Please help!

Interesting. This could explain why I'm seeing this as well.
http://support.microsoft.com/kb/973904

That error in the kb isn't supposed to happen with docx files, and opening the original file on my desktop doesn't trigger the error. Just when the file is uploaded to and then opened from wordpress.

My guess is that there's some mime type conversion happening such that when the webserver/browser reads the docx file it's using the doc mimetype.